Re: put library <body> at top-level

Re: put library <body> at top-level Tony Garnock-Jones 01 Dec 2005 06:15 UTC
Per Bothner wrote:
> I don't see any rationale for:
> (library <lib-path> <language>
>      <body>)
> rather than identitying a library with a file, as in:
> (library <lib-path> <language>)
> <body>

"Source code in files. How quaint. How 70's." (Kent Beck)

R5RS doesn't supply much detail about constructs such as files and
directories. They are implementation-specific, non-first-class
constructs that are vaguely mapped to ports by section 6.6. Neither
directories nor notions of file-system naming hierarchy are mentioned.

Scheme code doesn't have to live anywhere in particular - it can be
sourced from anywhere, from files, from stdin, from an email message,
from a database - the only constraint on scheme code is that it is an
S-expression.

List syntax is already suitable for sequencing S-expressions within an
S-expression. Files provide a second-class means of sequencing
S-expressions. Recovering a complete list of S-expressions from a file
requires some small-but-nonzero amount of work.

A file is not always the best granularity for a library - sometimes many
small libraries are best expressed in a single file, and sometimes a
single library is best expressed in multiple files.

The scoping of the |library| form can be unclear if forms /following/
the declaration are to be considered part of the library:

  (library "mylib" "scheme://r6rs")
  (define library (compose write list))
  (library "otherlib" "scheme://r6rs")
  (define number 17)

Regards,
  Tony